1. Field of the Invention
The present invention relates to time delay extension furnished by electromagnetic relays and supercapacitors, and more particularly to a linear adjustment of time delay extension and time of activation from just three electronic components.
2. Related Art
An electronic timer generally requires a timing circuit such as vibrator circuits consisting of resistors, capacitors, diodes, inductors, comparators and transistors, etc., to achieve the desired period of time or timing sequence. For good unit-to-unit repeatability or large time extension ranges, the circuits demand the use of closely matched transistors and capacitors, or timing capacitors with low leakages. In U.S. Pat. No. 3,970,899, which is incorporated herein as reference, a time delay extender that is an improved design over his previous version of multivibrator circuit is taught. Since the U.S. Pat. No. 3,970,899 employed many expensive and bulky electronic components for the extender, it does not satisfy features with the current trend of miniaturization, lightweight and low-cost of today""s electronic devices.
Supercapacitors are energy-storage devices with energy densities higher than those of conventional capacitors, and power densities higher than those of all known batteries. Because of the dual characteristics, supercapacitors may be used as a back-up power like what the batteries do, as disclosed in U.S. Pat. No. 5,608,684 for long-term data preservation in random access memory (RAM) and read only memory (ROM), devices consuming low currents from xcexcA to a few mAs. On the other hand, supercapacitors may deliver or accept peak currents of hundreds A, for example in electric vehicles as taught in U.S. Pat. No. 6,222,334 issued to Tamagawa et al. where the particular capacitors are included in a regenerative braking system to collect waste energy. Both U.S. Pat. Nos. 5,608,684 and 6,222,334 are incorporated herein as reference.
The instant invention presents a novel application of supercapacitors in conjunction with electromagnetic relays to form a time delay extender or an actuator, which may be used for extended illumination in garages, warehouses, hallways, homes, office and interior of automobiles, as well as in security monitoring systems, also in actuating systems after a main power therein is turned off. Duration of time delay extension or time of activation is determined collectively by both the capacitance of supercapacitors and the current consumption of relays. When an adjustable resistor is incorporated with the precedent elements, the new circuit can provide a linear adjustment of time extension or time activation. Due to the small sizes, simplicity and ruggedness of the three components proposed by the present invention, the aforementioned electronic timer is light, compact, reliable, and easy of installation and operation.
The invention provides a circuit of an electronic timer powered by an external power source, wherein the electronic timer controls a connection switch, which allows the external power source to provide a power to a load through the switch. The circuit comprises: an adjustable resistor; a capacitor with sufficiently large capacitance connected to the resistor in parallel; and an electromagnetic relay, connected to the capacitor in parallel to form the electronic timer, wherein the relay controls the connection switch to an on state or an off state.
In the foregoing description, the external power source charges the capacitor and activates the rely to set the switch at the on state, whereby the external power source also provides the power to the load when the switch is at the on state.
When the external power source stops powering the electronic timer, the capacitor then activates the rely to maintain the switch at the on state for a duration, wherein the adjustable resistor can be used to adjust the duration.